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Command injection in Ruby Gem Webbynode

From: Larry W. Cashdollar (larry0me.com)
Date: Sat Dec 14 2013 - 19:09:24 CST

Title: Command injection in Ruby Gem Webbynode

Date: 11/11/2013

Author: Larry W. Cashdollar, _larry0

Download: http://rubygems.org/gems/webbynode

Vulnerability Description:
The following code located in: ./webbynode- doesn't fully sanitize user supplied input before passing it to the shell via %x.

Messages via the growlnotify command line can possibly be used to execute shell commands if the message contains shell meta characters.

def self.message(message)
if self.installed? and !$testing
  message = message.gsub(/\x1B\[([0-9]{1,2}(;[0-9]{1,2})?)?[m|K]/, "")
  %x(growlnotify -t "#{TITLE}" -m "#{message}" --image "#{IMAGE_PATH}")

The message.gsub regex strips ANSI encoded characters from the #{message} variable, it doesn't strip characters like ;&| etc. If the attacker can control the contents of #{message}, #{TITLE} or #{IMAGE_PATH} they can possibly inject shell commands and execute them as the client user.

Vendor: Notified 11/11/2013

I also submitted a pull request

Advisory: http://www.vapid.dhs.org/advisories/webbynode-command-inj.html